Production and accumulation of Beta-hydroxy fatty acids and alpha, beta-unsaturated fatty acids during fatty acid beta-oxidation by isolated rabbit heart mitochondria and by aerobic and ischemic isolated perfused rabbit heart will be measured. Gas liquid chromatography-mass spectrometry will be used to identify and measure these fatty acids. Production of these beta-oxidation intermediates will be correlated with beta-oxidation flux and the degree of ischemia (heart). The effect of these beta-oxidation intermediates on mitochondrial respiration and adenine nucleotide transferase activity will be determined.